The invention relates to a method for setting a packer in a well bore, wherein a production tubing with a packer is located in the well bore, and the packer is set by a radial expansion of packing means of the packer, for sealing between the packer and the well bore wall.
The invention also relates to a packer to be included in a production tubing in a well bore, comprising a body with radially expandable packing means, for sealing between the packer and the well bore wall.
In recovery of hydrocarbons from hydrocarbon reservoirs, wells are drilled from the seabed or the surface of the earth, down to the reservoir. The wells are lined with pipes designated casing to prevent the well from collapsing. A production packer is placed in the lower end of the casing, above the reservoir, and a pipe designated production tubing is placed inside the casing, through the production packer, for conveying the hydrocarbon flow from the reservoir to the surface.
Some wells are drilled through one or more reservoirs. In such wells the tubing normally extends to the lower reservoir. In order to control the inflowing from each reservoir, and sometimes also at different places in the same reservoir, inlet valves are included in the tubing at the desired locations. In order to obtain an effective use of the inlet valves, it is required to prevent hydrocarbons from flowing along the outside of the tubing, and therefore the space between the tubing and the well bore wall is either filled with concrete or sealed by a packer between each inlet valve. Such a packer is known as an xe2x80x9cexternal casing packerxe2x80x9d. Whether the pipe in the reservoir area is designated casing or tubing is a matter of terminology, or the configuration of the well, and such a packer may thus as well be called an xe2x80x9cexternal tubing packerxe2x80x9d. The tubing consist of sections which are screwed together, and each end of the packer has threads, in order to be screwed in between two tubing sections. The packers are set by expanding packing means of the packer, which is done by a tool which is lowered into the packer and connected to the packer for manipulating the packing means.
A known external casing or tubing packer consist of a hollow rubber element, which is inflated by a fluid, e.g. concrete, which is injected by the tool. After injection, the concrete sets and keeps the rubber element in the inflated position, in which it seals between the tubing and the well bore wall. This type of packer is encumbered with the drawback that the rubber element may be damaged during the installation or inflation. Further the temperature, pressure and well fluids adversely influence the integrity of the rubber, and therefor the lifetime of such a packer is often shorter than desired. Therefore, this type of packer is likely to leak.
In a production packer, and other packers intended for sealing between the inner tubing and the outer casing, the sealing is achieved by radially expandable mechanical packing means, which may be hydraulically activated by a tool which is lowered into the packer. Here the above mentioned problems related to the inflatable rubber element do not exist. These packers, do, however, require that the outer contact surface, i.e. the inside of the casing, is circular. Although a well is drilled by a circular bit, the well bore wall is far less circular than the inside of the casing. Known packer designs which are intended for sealing between the tubing and the casing are therefore unsuitable to establish a proper seal between the tubing and the well bore wall.
U.S. Pat. No. 4,057,118 A describes a packer comprising a body with radially packing means for sealing between the packer and the well bore wall, wherein the packer has rotatable connections between the body and the tubing.
U.S. Pat. No. 4,057,118 A further describes a method for setting a packer in a well bore, wherein a tubular member with a packer is located in the well bore.
The object of the invention is to provide a method for setting a packer and a packer in which the above problems related to leakage are reduced or eliminated.
The objects are achieved according to the invention with a method and a packer of the type mentioned in the introduction which are characterized by the features which are stated in the independent claims.
The invention thus relates to a method for setting a packer in a well bore, wherein a production tubing with a packer is located in the well bore, and the packer is set by a radial expansion of packing means of the packer, for sealing between the packer and the well bore wall. When setting the packer, radially expandable abrading means of the packer are radially expanded and rotated. This causes an abrading, i.e. a milling or grinding, of the well bore wall, and thus a rounding of the well bore wall. Further the radially expandable packing means are expanded against the rounded well bore wall. The packing means thereby establishes a seal between the packer and the well bore wall in which the above mentioned problem related to leakage between radially expandable packing means and a not circular outer contact surface, i.e. the well bore wall, is reduced or eliminated.
The invention also relates to a packer to be included in a production tubing in a well bore, comprising a body with radially expandable packing means, for sealing between the packer and the well bore wall. The packer comprises radially expandable abrading means, expander means for radially expanding the abrading means, rotatable connections between the packer body and the production tubing, and gripping means for an operational connection between the packer body and an external rotating means. A radial expansion of the abrading means and a rotation of the packer body, i.e. a rotation of the abrading means, causes a rounding of the well bore wall.
The packing means and the abrading means may thus be formed by separate elements, which are radially expanded by separate mechanisms. The abrading means may be radially expanded prior to the expanding of the packing means. This allows a removal of cuttings from the rounding of the well bore wall prior to the expanding of the packing means. A removal of the cuttings can be done mechanically or by flushing with a flushing fluid which is externally supplied.
Alternatively the packing means may be radially expanded simultaneously with the radial expanding and rotating of the abrading means. The rounding of the well bore wall may then be done by abrading lugs arranged on the packing means, i.e. the packing means and the abrading means are constituted by the same elements. This enables a simple and compact design. The cuttings may be removed in the longitudinal direction by the abrading lugs being arranged in at least one helical pattern on the packing means.
Instead of removing the cuttings, the cuttings may be pressed against the well bore wall by the packing means, the cuttings thereby forming a seal cake.
The packer may have an elastic seal on the outside of the packing means, underneath the abrading lugs. When radially expanding the packing means, the elastic seal will also be radially expanded. Depending on whether the cuttings are removed or maintained in place, the elastic seal will be pressed between the packing means and the well bore wall or the seal cake made from the cuttings, respectively. The elastic seal distributes the pressure from the packing means and ensures a proper sealing.
The rotatable connections between the packer body and the production tubing may be formed by threaded connections between the tubing and packer end portions, and swivels between the packer end portions and the packer body.
The rotating means for rotating the packer body may be a rotational tool which is lowered into the well bore and operationally connected to the packer body. This operational connection may be carried out by lowering the rotational tool into the packer, and radially expanding gripping means of the rotational tool against the inside of the packer body.
Other ways of rotating the packer body are also conceivable, e.g. a rotation by the drill string.
The expander means may comprise a hydraulic cylinder and piston on each side of the radially expandable packing means, and a hydraulic fluid supply to the cylinders for generating a longitudinal movement of the pistons. These pistons may be connected to coacting conical surfaces which are connected to or constitute the radially expandable packing means/abrading means, and which by the longitudinal movement of the pistons provide a radial expansion of the packing means. The packer may have ratchet means in order to prevent the return of the packing means from a radially expanded position. The hydraulic fluid supply to the cylinders may be adapted to connect to a mating hydraulic fluid supply from the rotational tool.